The invention relates to colloids containing particles of amorphous borosilicate.
Borosilicates are compounds of the formula nB2O3xc2x7m(SiO2). The bonds between the atoms of a borosilicate are usually represented:
xe2x95x90Bxe2x80x94Oxe2x80x94Sixe2x89xa1.
Known methods of manufacturing borosilicates include:
1) fusing suitable boron and silicon oxides at high temperatures to form compounds containing boron-oxygen-silicon bonds,
2) combining appropriate boron and silicon compounds under anhydrous conditions to form compounds containing boron-oxygen-silicon bonds, or
3) using both high temperatures and anhydrous conditions to make borosilicates.
In order to obtain stable boron-oxygen-silicon bonds, borosilicates made using these known methods are either crystalline or glass.
According to Iler, The Chemistry of Silica, (copyright)1979 by John Wiley and Sons, Inc., page 410, xe2x80x9cthe Sixe2x80x94Oxe2x80x94B bond is hydrolytically unstablexe2x80x9d. Further discussion on this point can be found in the article by Irwin et al., in Journal of Non-Crystalline Solids, 89 (1987) 191-205, entitled, xe2x80x9cSpectroscopic Investigations of Borosiloxane Bond Formation in the Sol-Gel Process.xe2x80x9d On page 192 of the Irwin et al. article, it is stated, xe2x80x9cIn fact, borosiloxane bonds are known to be very easily broken by hydrolysis, and we know of no examples in the chemical literature where a xe2x95x90Bxe2x80x94Oxe2x80x94Sixe2x89xa1 containing compound is synthesized under other than anhydrous conditions.xe2x80x9d As stated previously, borosilicates formed in these high temperature and anhydrous processes have bonds that are hydrolyzable. As stated on page 197 of the Irwin et al. article, xe2x80x9cBorosiloxane groups are known to be highly reactive toward hydrolysis, and are easily cleaved by water under neutral, acidic or basic conditions.xe2x80x9d The fact that the bonds in crystalline borosilicates are hydrolyzable means that the use of crystalline borosilicates in aqueous systems is limited. The fact that borosiloxane (Bxe2x80x94Oxe2x80x94Si) bonds are readily hydrolyzed has to date restricted the synthesis and use of aqueous colloids comprising borosilicate particles as well.
U.S. Pat. No. 4,902,326 issued to Jarmon discloses the use of a colloidal suspension of inorganic particles to make a fiber reinforced-glass matrix composite article. The source of colloids useful in the invention of Jarmon is not disclosed in the Patent, except for the xe2x80x9ccolloidal silicaxe2x80x9d being identified as Ludox(trademark)AS-40. Ludox(trademark)mAS-40 is an ammonium stabilized colloidal suspension of silica, not a colloid comprising amorphous borosilicate particles. There is no enablement for the xe2x80x9caqueous colloidal suspension of borosilicatesxe2x80x9d alleged to be useful in the invention of Jarmon. Furthermore, the invention of Jarmon is not an aqueous system where the boron-oxygen-silicon bond is going to be a limiting factor. Accordingly, any colloid used in the invention of Jarmon does not require non-hydrolyzable bonds.
Because of the desirability of using borosilicates in aqueous systems, it would be desirable to have a borosilicate composition of matter that is capable of retaining its functionality in aqueous systems without the bonds between the atoms being hydrolyzed.
The invention is a colloid comprising particles of amorphous borosilicate, wherein said particles of amorphous borosilicate are not borosilicate glass.